CodeRunner Documentation (V3.0.0)

4.2 Built-in question types

The file <moodlehome>/question/type/coderunner/db/builtin_PROTOTYPES.xml is a moodle-xml export format file containing the definitions of all the built-in question types. During installation, and at the end of any version upgrade, the prototype questions from that file are all loaded into a category CR_PROTOTYPES in the system context. A system administrator can edit those prototypes but this is not generally recommended as the modified versions will be lost on each upgrade. Instead, a category LOCAL_PROTOTYPES (or other such name of your choice) should be created and copies of any prototype questions that need editing should be stored there, with the question-type name modified accordingly. New prototype question types can also be created in that category. Editing of prototypes is discussed later in this document.

Built-in question types include the following:

  1. c_function. This is the question type discussed in the above example. The student supplies just a function (plus possible support functions) and each test is (typically) of the form

    printf(format_string, func(arg1, arg2, ..))

    The template for this question type generates some standard includes, followed by the student code followed by a main function that executes the tests one by one.

    The manner in which a C program is executed is not part of the question type definition: it is defined by the particular sandbox to which the execution is passed. The Jobe sandbox uses the gcc compiler with the language set to accept C99 and with both -Wall and -Werror options set on the command line to issue all warnings and reject the code if there are any warnings.

  2. python3. Used for most Python3 questions. For each test case, the student code is run first, followed by the test code.

  3. python3_w_input. A variant of the python3 question in which the input function is redefined at the start of the program so that the standard input characters that it consumes are echoed to standard output as they are when typed on the keyboard during interactive testing. A slight downside of this question type compared to the python3 type is that the student code is displaced downwards in the file so that line numbers present in any syntax or runtime error messages do not match those in the student's original code.

  4. python2. Used for most Python2 questions. As for python3, the student code is run first, followed by the sequence of tests. This question type should be considered to be obsolescent due to the widespread move to Python3 through the education community.

  5. java_method. This is intended for early Java teaching where students are still learning to write individual methods. The student code is a single method, plus possible support methods, that is wrapped in a class together with a static main method containing the supplied tests (which will generally call the student's method and print the results).

  6. java_class. Here the student writes an entire class (or possibly multiple classes in a single file). The test cases are then wrapped in the main method for a separate public test class which is added to the students class and the whole is then executed. The class the student writes may be either private or public; the template replaces any occurrences of public class in the submission with just class. While students might construct programs that will not be correctly processed by this simplistic substitution, the outcome will simply be that they fail the tests. They will soon learn to write their classes in the expected manner (i.e. with public and class on the same line, separated by a single space)!

  7. java_program. Here the student writes a complete program which is compiled then executed once for each test case to see if it generates the expected output for that test. The name of the main class, which is needed for naming the source file, is extracted from the submission by a regular expression search for a public class with a public static void main method.

  8. octave_function. This uses the open-source Octave system to process matlab-like student submissions.

  9. php. A php question in which the student submission is a normal php file, with PHP code enclosed in tags and the output is the usual PHP output including all HTML content outside the php tags.

As discussed later, this base set of question types can be customised or extended in various ways.

C++ isn't available as a built-in type at present, as we don't teach it. However, as the Jobe server is by default configured to run C++ jobs (using the language ID 'cpp') you can easily make a custom C++ question type by starting with the C question type, setting the language to cpp and changing the template to include iostream instead of, or as well as, stdio.h. The line

    using namespace std;

may also be desirable.